Walls of the vasculature, particularly arterial walls, may develop areas of weakness and/or dilatation called aneurysms. The rupture of certain aneurysms, for example abdominal aortic aneurysms and brain or cerebral aneurysms in the neurovasculature, can cause hemorrhage and death. Aneurysms are generally treated by excluding the weakened part of the vessel from the arterial circulation. For treating a cerebral aneurysm, such exclusion may be accomplished by: (i) surgical clipping, where a metal clip is secured around the base of the aneurysm; (ii) packing the aneurysm with small, flexible wire coils (micro-coils); (iii) using embolic materials to “fill” an aneurysm; (iv) using detachable balloons or coils to occlude the parent vessel that supplies the aneurysm; and/or (v) intravascular stenting, including flow-diverter therapy.
Stents include generally tubular prostheses that expand radially or otherwise within a vessel or lumen to provide therapy or support against blockage of the vessel. Stents of various construction may be utilized, including balloon expandable metal stents, self-expanding braided metal stents, knitted metal stents, coiled stents, rolled stents, and the like. Stent-grafts are also used, which include a tubular graft material supported by a metallic stent.
Coatings have been applied to medical devices to impart lubricious and/or anti-adhesive properties and serve as depots for bioactive agent release. As medical devices, especially those possessing irregular and/or rough surfaces, may be conducive to thrombus formation, coatings may be applied to these medical devices to reduce the formation of thrombi. Adherence of these coatings to the substrate used to form the device may prove difficult, with delamination occurring in some cases.